Application of coating based on 5 nm octadecylamine-functionalized gold-nanoparticles for protecting the spin-polarization of atoms confined in a vacuum cell

We report on the expressed atomic spin-polarization protection properties of thin layers of Octadecylamine capped gold-nanoparticles applied to the inner surface of an alkali metal vapor cell. The work aims to reveal the potential of using appropriately functionalized gold nanoparticles as a novel approach to forming efficient coatings on the inner surface of vacuum cells for atomic spectroscopy. The performed layer characterization uses parameters of electromagnetically induced transparency/absorption resonances observed in the Hanle configuration. We show at the Rb D2 absorption line that cells with such a coating provide conditions for achieving high-contrast and narrow, bright, and dark resonances, comparable to those reported by others for Octadecyltrichlorosilane coatings. Using visualization software for structural analysis, we represent the possible interaction scenarios between the alkali atoms and the surface building blocks. We demonstrate and discuss the main structural and functional differences introduced by covering the cell surface with passivated nanoparticles instead of directly using molecules to form monolayers. Having gold-nanoparticles in the coating allows preserving at the same time the earlier discovered advantage for high-speed control over the Rb vapor density by light-induced desorption of atoms. That enables significant problem-solving in atomic clocks and magnetometers and eases their considerable miniaturization.